Copper ore process control



May 19, 1970 F. L. HOLDERREED ETAL COPPER ORE PROCESS CONTROL Filed Sept. 26, 1967 PROGRAM UNIT l I f 1 I7 l 1 i m. I l7 l6 I I? I6 TITRATOR j i R v is l v A I l w 1 7 I l6 g L /22 s29 PROGRAM UNIT A I I I I Q at 28 FIG. 2 I i? 2i 1 T I I l v I E V 26 ATOMIC 9 J i 28 ABSORPTION r I l SPECTROMETER 27 INVENTORS F. L. HOLDER REED WILLIAM LUCY BY LAUTARO s. DIAZ United States Patent US. Cl. 75-1 12 Claims ABSTRACT OF THE DISCLOSURE Method and apparatus for automatically controlling any multi-flow stream copper ore processing operation. A plurality of ore process flow stream are periodically sampled and the samples are presented in sequence to an automatic analyzer capable of generating an electric signal proportional to the concentration of a substance in a sample. The electric signal is sequentially transmitted to a series of electrically operated control valves to regulate the addition of process reagent to the flow streams.

CROSS-REFERENCE TO RELATED APPLICATION This is a continuation-impart of application Ser. No. 455,890 filed May 14, 1965, now abandoned.

BACKGROUND OF THE INVENTION This invention relates to copper ore processing and more particularly to method and apparatus for automatically controlling a copper ore processing operation having a plurality of ore processing flow streams.

Modern copper ore concentration is a complex operation, involving the various steps of crushing, grinding, flotation, regrinding, LPF, cleaning, recleaning, and scavenging. In a large copper concentrator thousands of tons of ore are processed each hour. Unless accurate and precise control of each step in the ore processing is maintained, a high percentage of copper recovery cannot be reliably obtained, and economic operation of the concentrator is impossible.

In the past the method of controlling such a copper ore processing operation was to cut samples from the various process streams, filter the samples to reclaim the solids content and assay the solids by conventional wet-assay methods. The assay information determined in this manner was not available until from two to twenty-four hours after the cutting of the sample, and by this time the parameters of the process had, in all likelihood, altered so significantly that any changes made in the processing based on the sample assay results would be useless or even harmful.

More recently, accurate analyzing instruments have been devised to permit immediate sample assay and analysis. In a typical system a sample is cut from a copper ore process stream and pumped to the analyzer, giving the operator of the process immediately an indication of the sample contents and permitting an accurate record of sample analysis to be maintained. Such analyzers include automatic titrators to give an indication of the relative alkalinity of a sample, and automatic radiation assaying units which involve exciting the sample to be assayed so that it emits (or absorbs) radiation characteristic of the elements to be determined, and then analyzing and measuring such emitted (or absorbed) radiation to ascertain the quantity of such elements that are present in the sample. Examples of this latter type of analyzer are X-ray radiation apparatus and atomic absorption spectrometers.

While these advances in assaying instrumentation have been most useful it has still been necessary for the operator of the process to evaluate the results of this on-stream 3,512,956 Patented May 19, 1970 "ice analysis and determine if any changes in the process were required. If the operator decided that certain ore processing parameters should be altered he then would initiate the change, as, for example, by increasing or decreasing the addition of a process reagent to one of the process flow streams.

Because of the high rate of ore processing and the multiplicity of ore processing flow streams and control factors, such a system could not control the ore processing operation in any optimal fashion. The reaction time of one or more operators to the swiftly changing factors of the process was too great to utilize effectively the sophisticated automatic analyzing equipment instrumentation technology has made available.

We have discovered and devised a system for eifectively and automatically controlling a copper ore processing operation having a multiplicity of copper ore process flow streams. The system includes a sample cutting mechanism for periodically cutting a sample from each of the flow streams in sequence. Each of these samples is passed or pumped through conduits to a centrally located automatic analyzer which is capable of generating an analog electric signal proportional to the concentration of an element or a substance in the sample. A control device is provided for each of the flow streams to regulate the addition of a process reagent such as lime or sponge iron to the flow stream. In the preferred embodiment of our invention this control device is an electro-pneumatic controlled valve operating on a periodic open-closed cycle. The system further provides for the transmission of the electric signal from the automatic analyzer to each of the control devices in sequence where electric circuitry is provided to transform the electric analog signal to an electric pulse suitable for regulating the control device.

In this fashion an automatic and periodic sampling of each of the flow streams in the ore processing operation may be made, the samples analyzed in sequence and the results of the analysis utilized to control immediately the addition of a process reagent to the appropriate flow stream. The appropriate flow stream would usually, but not necessarily in our system, be the same flow stream from which the sample just analyzed had been cut.

Our invention permits the immediate and effective control of a copper ore concentrator before the process factors have had a chance to alter significantly. The control of the copper ore processing therefore becomes for the first time a truly meaningful and exact operation. Moreover, our system permits the continual, periodic control of a large number of flow streams. It should be obvious that more than one of the systems may be used in a copper ore processing operation to analyze the ore samples for different characteristics such as alkalinity, density or copper ion concentration. Thus our system makes possible the exact control of a copper concentrator relative to a number of process variables. The flow streams sampled and analyzed for one characteristic would, of course, not need to be the same as those sampled and analyzed for another characteristic. Moreover the rates of sampling may be different for each of the systems employed.

These and other objects and advantages of our invention will be more readily understood when the following description is read in connection with the accompanying drawing.

BRIEF DESCRIPTION OF THE DRAWING FIG. 1 is a schematic block diagram of a first embodiment of our invention which uses an automatic titrator;

and

FIG. 2 is a schematic block diagram of a second embodiment of our invention using an atomic absorption spectrometer.

3 DESCRIPTION OF THE PREFERRED EMBODIMENTS A first preferred embodiment of our invention, shown in FIG. 1, uses an automatic titrating unit to analyze the alkalinity of the copper ore processing flow streams and to control the addition of milk of lime to the flow streams, thus regulating the flow stream pH.

In a typical multistage flotation circuit for the recovery of copper, to which the present invention is applicable, the ore is initially submitted to a moderate primary grind and is then fed to a bulk float where the major separation of copper and gangue is made. The bulk tailing is final. After classifying in a cyclone and regrinding the bulk concentrate to further liberate copper mineral, a two-step cleaning section separates the permissible final concentrates from the middling particles. The final scavenging section is aimed at recovering only the middling copper from the previously liberated pyrite and gangue for retreatment and recycling to the cleaners. The scavenger tailing is also final.

In such an operation it is desirable to cut samples from several different streams in the flotation processes and to analyze the elemental content of the pulp in these streams so that close control can be maintained over the entire flotation operation. In the first preferred embodiment of our invention applied to the flotation circuit just described samples are cut from seven different process streams: the ore feed stream, the bulk tailing stream, the bulk concentrate stream, the concentrated streams of the first and second cleaners, and the scavenger concentrates and tailing streams.

The seven flow stream samples are pumped through seven conduits to an automatic sampling device 11. The sampling device 11 is preferably of the type described in US. Pat. No. 3,255,881 issued June 14, 1966 to P. L. Holderreed et al., titled Flotation Process Control. This sampler 11 periodically selects one of the seven continuously flowing sample streams 12 (indicated schematically by arrows in FIG. 1) in sequence at a preset rate. The flow stream selected by the sample cutter 11 is diverted into a sample measurement unit 13, being an overflow type sample measurement container. Material in excess of that needed for a sample is discarded.

The measurement unit 13 is connected by conduits to an automatic titration unit 14 which titrates each sample presented to it with reagent, measures the relative alkalinity of the sample and generates an analog electric signal 15 proportional to the alkalinity of the sample.

An electro pneumatic control valve 16 is provided for each of the process flow streams to be controlled. Each of these valves 16 regulates the addition of milk of lime to the process flow stream with which it is connected. In our preferred embodiment the valves operate in an open-closed cycle of 30 seconds, i.e., every 30 second cycle of valve operation the valve is opened for a period of time and closed for a period of time, the open/ closed ratio depending upon the electric control signal 17 actuating the valve 16. Thus, for example, if a signal 17 is an electric pulse of ten seconds duration the valve 16 remains open for ten seconds and closed for twenty seconds each half minute cycle of operation. If signal 17 is not present or present continually the valve 16 remains continuously closed or open, respectively.

Electrically connected to each of the control valves 16 is an electronic circuit !18 which is capable of transforming the electric analog signal 15 from the titrator 14 into a suitable electric signal 17 to operate the valve 16. Circuitry 18 in response to the analog signal 15 generates an electric pulse, the duration of this pulse in time being proportional to the amplitude of the analog signal 15. Electronic means to achieve this result are commercially available and are well known by those in the electronics art and will not be detailed here. Circuitry 18 also has means to store the result of this analog/pulse duration conversion for up to 60 minutes so as to con- 4 tinually present to the valve 16 every 30 seconds during that hour interval the latest control analog/pulse duration conversion. Every time a new signal 15 is transmitted to the circuitry '18 a new conversion is made and the old conversion determination is erased from the storage of circuitry 18.

An electronic programming unit 19 is provided to synchronize the operation of each of the units in the system. Thus, unit 19 periodically at a predetermined rate signals the sample cutter 11 to move on to the next flow stream 12 in the sequence. Unit 19 generates appropriately timed signals to control the transfer of the selected and measured sample from the measuring unit 13 to the automatic titrator 14. The programming device 19 also controls the transmission of the analog signal '15 to one of the circuit units 18 in sequence to control the valve 16 associated with the flow stream 12, a sample from which resulted in the instant signal 15. Various electronic means to achieve these results are also well known to electronic circuit designers, but electromagnetic stepping relays provide one convenient means of generating sequenced timing signals to the sampling unit 11, measuring unit 13, titrator 14 and circuits 18. The transmission of signal 15 to each of the circuits '18 in sequence can be accomplished by connecting the signal output of the titrator 14 in common to all of the circuits 18 and switching a gating signal from the programming unit 19 to each of the circuits 18 in turn thereby actuating its electronic conversion operation. Alternatively, the signal 15 can be connected to a rotary switch device in programmer 19 and from there distributed to each circuit 18 in sequence. Moreover, while separate circuit units 18 have been shown each associated with a control valve 16 it will be obvious that a single central circuit arrangement can be employed to perform the analog/pulse duration conversion, the results of each conversion being transmitted directly to the appropriate control valve 16.

A second embodiment of our invention is illustrated in FIG. 2. This arrangement is very similar to that system just described but instead of a titrator it employs an atomic absorption spectrometer to meaure the concentration of soluble copper in each sample presented to it and the addition of sponge iron to the flow streams is regulated instead of milk of lime.

An automatic sample cutter 21 is provided to select one of seven continuously flowing samples from among the seven flow streams 22 (shown schematically by four arrows in FIG. 2) to which the sample cutter 21 is attached. The sample selected is diverted into a measuring unit 23 similar to that described in connection with the first embodiment, from which it proceeds into a manipulating unit 24 in which the pulp or solution sample is automatically manipulated, leached if necessary, conditioning reagents added and the sample is filtered prior to presentation to an automatic atomic absorption spectrometer 25. The spectrometer 25 analyzes each sample presented to it and generates an analog signal 26 proportional to the concentration of dissolved copper ion present in the sample. The signal 26 is then distributed to one of the circuit devices 27 electrically connected to a control valve 28 which regulates the addition of sponge iron to precipitate copper from the solution of the appropriate flow stream. The circuit elements 27 perform the analog/pulse duration conversion on signal 2 6 and actuate the electro pneumatic valves 28 in the same manner as described previously. A programming unit 29 is provided as before to generate the timing signals necessary to synchronize and control the operation of the units of the system. Programmer 29 controls the selection of sample, its measurement, the operation of the manipulating unit 24 and the spectrometer 25. It also controls the transmission of signal 26 so that the valve 28 corresponding to the flow stream being sampled is actuated.

While seven flow streams have been shown being sampled in the first and second embodiments it will be understood that the number of flow streams which can be sampled or the rate at which they can be sampled is limited only by the design of the equipment used. Further more, in both embodiments all of the sample streams presented to the sample cutters 11 and 21 need not be selected but groups of stream inputs can be ignored or skipped over in the sequencing if, for example, the ore processing operation is running at less than full plant operation.

While the signals generated by the automatic analyzer in this invention are used to control the operation of regulating devices the signals may also simultaneously be transmitted to recording devices and electronic computers for process record and calculation purposes.

As mentioned at the outset, the eifective control of a copper ore processing operation can properly include the utilization of a plurality of the systems of our invention, each employing a ditferent analyzer device to control a different aspect of system operation.

It will be understood that various changes in the details, materials, steps and arrangement of units which have been herein described and illustrated in order to explain the nature of our invention may be made by those skilled in the art within the principle and scope of the invention as expressed in the appended claims.

We claim:

1. Apparatus for automatically controlling a copper ore processing operation having a plurality of ore processing flow streams comprising:

(a) sampling means for periodically cutting a sample from each of the flow streams in sequence;

(b) an automatic analyzer capable of producing an electric signal proportional to the concentration of a predetermined substance in a sample presented to the analyzer;

(c) conduit means connecting the sampling means with the analyzer whereby each sample is presented in sequence to the analyzer;

(d) a plurality of control devices, each device being associated with one of the flow streams, for controlling the addition of a process reagent to the flow streams;

(e) circuit means for transmitting the electric signal to each of the control devices in sequence to actuate each control device.

2. Apparatus for automatically controlling copper ore processing operation having a plurality of ore processing flow streams comprising:

(a) sampling means for periodically cutting a sample from each of the flow streams in sequence;

(b) an automatic analyzer capable of generating an electric analog signal proportional to the concentration of a predetermined substance in a sample presented to the analyzer;

(c) conduit means connecting the sampling means with the analyzer whereby each sample is presented to the analyzer in sequence;

((1) a plurality of electrically operated control devices, each device being associated with one of the flow streams, for controlling the addition of a process reagent to the flow streams;

(e) a plurality of circuit means for converting an analog signal to an electric pulse suitable for operating the control devices, each of the circuit means being connected to one of the control devices; and

(f) switching means for transmitting the electric analog signal from the analyzer to each of the circuit means in sequence.

3. Apparatus for automatically controlling a copper ore processing operation having a plurality of ore processing fioW streams comprising:

(a) sampling means for periodically cutting a sample from each of the flow streams in sequence;

(b) an automatic titrator capable of producing an electric signal proportional to the alkalinity of a sample presented to the titrator;

(c) conduit means connecting the sampling means with the titrator whereby each sample is presented in sequence to the titrator;

(d) a plurality of control devices, each device being associated with one of the flow streams for controlling the addition of a process reagent to the flow streams;

(e) circuit means associated with each of the control devices for converting an electric analog signal to an electric pulse signal for actuating and control devices;

(f) means for transmitting the electric signal from the titrator to each of the circuit means in sequence.

4. Apparatus for automatically controlling a copper ore processing operation having a plurality of ore processing flow streams comprising:

(a) sampling means for periodically cutting a sample from each of the flow streams in sequence;

(b) an automatic atomic absorption spectrometer capable of producing an electric signal proportional to the concentration of acid soluble copper in a sample presented to the spectrometer;

(c) conduit means for connecting the sampling means to the spectrometer whereby each sample is presented in sequence to the spectrometer;

(d) a plurality of control devices, each device being associated with one of said flow streams, for controlling the addition of a process reagent to the flow streams;

(e) means for transmitting the electric signal to each of the control devices in sequence.

5. Apparatus for automatically controlling a copper ore processing operation having a plurality of ore processing flow streams comprising:

(a) sampling means for periodically cutting a sample from each of the flow streams in sequence;

(b) treatment means associated with the sampling means for adding at least one conditioning reagent to each sample;

(c) an automatic atomic absorption spectrometer capable of generating an electric signal proportional to the concentration of acid soluble copper in a sample presented to the spectrometer;

(d) conduit means connecting the sampling means with the spectrometer whereby each sample is presented in sequence to the spectrometer;

(e) a plurality of control devices, each device being associated with one of the flow streams, for controlling the addition of a process reagent to the flow streams;

(f) circuit means for transmitting the electric signal to and actuating each of the control devices in sequence.

6. A system for controlling a copper ore processing operation comprising more than one of the apparatus described in claim 1.

7. A method for automatically controlling a copper ore processing operation having a plurality of ore processing 60 flow streams comprising the steps of:

(a) periodically cutting a sample from each of the flow streams in sequence;

(b) presenting each of the samples in sequence to an automatic analyzer capable of generating an electric analog signal proportional to the concentration of a predetermined substance in a sample presented to the analyzer; and

(c) transmitting the electric analog signal in sequence to each of a plurality of control devices, each device being associated with one of the flow streams to regulate the addition of a process reagent to the flow streams. 8. A method for automatically controlling a copper ore processing operation having a plurality of ore processing flow streams comprising the steps of:

(a) periodically cutting a sample from each of the flow streams in sequence;

(b) presenting each of the samples in sequence to an automatic analyzer capable of generating an electric analog signal proportional to the concentration of a predetermined substance in a sample presented to the analyzer;

(c) instantaneously transmitting the electric analog signal to one of a plurality of control devices, each device being associated with one of the flow streams to regulate the addition of a process reagent to the flow stream associated with the control device; and

(d) periodically switching the electric analog signal to the next control device in sequence.

9. A method for automatically controlling a copper ore processing operation having a plurality of ore processing flow streams comprising the steps of:

(a) periodically cutting a sample from each of the flow streams in sequence;

(b) presenting each of the samples to an automatic analyzer capable of generating an electric analog signal proportional to the concentration of a predetermined substance in a sample presented to the analyzer;

(c) instantaneously transmitting the analog signal to one of a plurality of control devices, each device being associated with one of the flow streams;

(d) converting the analog signal to an electric pulse suitable for actuating the control device to regulate the addition of a process reagent to the flow stream associated with the control device; and

(e) periodically switching the analog signal to the next control device in sequence.

10. A method for automatically controlling a copper ore processing operation having a plurality of ore processing flow streams comprising the steps of:

(a) periodically cutting a sample from each of the flow streams in sequence;

(b) presenting each of the samples in sequence to an automatic titrator capable of generating an electric signal proportional to the alkalinity of a sample presented to the titrator; and

(c) transmitting the electric signal in sequence to each of a plurality of control devices, each device being associated with one of the flow streams, to regulate the addition of a process reagent to the flow streams.

11. A method for automatically controlling a copper ore processing operation having a plurality of ore processing flow streams comprising the steps of:

(a) periodically cutting a sample from each of the flow streams in sequence;

(b) presenting each of the samples in sequence to an automatic atomic absorption spectrometer capable of generating an electric analog signal proportional to the concentration of acid soluble copper in a sample presented to the spectrometer; and

(c) transmitting the electric signal in sequence to each of a plurality of control devices, each device being associated with one of the flow streams to regulate the addition of a process reagent to the flow streams.

12. A method for automatically controlling a copper ore processing operation having a plurality of ore processing flow streams comprising the steps of:

(a) periodically cutting a sample from each of the flow streams in sequence;

(b) manipulating each sample by adding at least one conditioning reagent and filtering the sample;

(0) presenting each of the samples in sequence to an automatic atomic absorption spectrometer capable of generating an electric analog signal proportional to the concentration of acid soluble copper in a sample presented to the spectrometer; and

(d) transmitting the electric analog signal in sequence to each of a plurality of control devices, each device being associated with one of the flow streams, to regulate the addition of a process reagent to each of the flow streams in sequence.

References Cited UNITED STATES PATENTS 2,770,531 11/1956 Hawes et al. 23-230 3,073,682 1/1963 Lindsley 23--230 3,104,941 9/1963 Hart et al. 23--230 XR 3,158,163 11/1964 Claudy 23-230 XR 3,255,881 6/1966 Holderreed et al 2091 OTHER REFERENCES Savas, Computer Control of Industrial Processes, 1965, pp. 352 and 378.

MORRIS O. WOLK, Primary Examiner d R. E. SERWIN, Assistant Examiner US. Cl. X.R. 2325 3, 230 

